Kindle Deals
Some overlap here, but for $50 you could pick up 20-25 great books. Selections from Aaron Hughes, Nathan Bingham, and Tim Challies. One of the great things about the Kindle for Mac App is the way you can copy and paste into a Word document, a great help when you’re trying to preserve the fruits of your study for future reference. More recent Kindle books will also give you automatic references for footnotes, etc.